Glycol ether-chromium corrosion resistant coatings for metallic surfaces

ABSTRACT

A PROCESS AND COMPOSITION FOR NCREASING THE RESISTANCE TO CORROSION OF A METALLIC SURFACE, WHICH PROCESS COMPRISES CONTACTING SAID METALLIC SURFACE WITH A COMPOSITION OBTAINED BY MIXING IN THE PRESENCE OF WATER A WATER SOLUBLE CHROMIUM COMPOUND SUCH AS CHROMIUM TRIOXIDE, AMMONIUM CHRMATE, CHORMIUM CHROMATE, AND THE LIKE, AND AN OXYGENATED ORGANIC COMPOUND HAVING THE FOLLOWING FORMULA:   R1-O-(CH(-R2)-CH(-R2)-O)N-R3   WHEREIN R1 IS AN ALKYL GROUP HAVING FROM 1 TO 6 CARBON ATOMS, R2 IS HYDROGEN OR AN ALKYL GROUP HAVING FROM 1 TO 6 CARBON ATOMS, AND R3 HYDROGEN OR AN ALKYL GROUP HAVING FROM 1 TO 6 CARBON ATOMS, N IS AN INTERGER OF FROM 1 TO 4.

United States Patent 3,679,493 GLYCOL ETHER-CHROMIUM CORROSION RE- SISTANT COATINGS FOR METALLIC SURFACES John Paul Gerhardt Beiswanger, Easton, and Assadullah Nassry, Bethlehem, Pa, assignors to GAF Corporation, New York, N.Y. No Drawing. Filed Mar. 11, 1970, Ser. No. 18,762 Int. Cl. C23f Z/26, 11/16 US. Cl. 148-616 21 Claims ABSTRACT OF THE DISCLOSURE A process and composition for increasing the resistance to corrosion of a metallic surface, which process comprises contacting said metallic surface with a composition obtained by mixing in the presence of water a water soluble chromium compound such as chromium trioxide, ammonium chromate, chromium chromate, and the like, and an oxygenated organic compound having the following formula:

FIELD OF THE INVENTION The instant invention relates to a composition useful in increasing the corrosion resistance of metallic surfaces and a process for protecting metallic surfaces by the application of such compositions thereto. In particular, the instant invention is directed to the use of a composition comprising a chromium compound and an oxygenated organic compound ('I) to increase the corrosion resistance of metallic surfaces.

PRIOR ART Heretofore, a number of surface treating processes have been proposed in order to solve a problem in connection with the corrosion resistance or adherence of finish coatings to the metal surface. For example, it is known that the phosphating treatment involving the use of a phosphate solution, such as, iron, zinc, manganese or calcium phosphate, or an electrolytic treatment in a phosphate or chromate solution with an alternating or direct electric current, will afiord some measure of corrosion resistance. Although the above processes have attained some measure of corrosion resistance, ease of adaptability for commercial fabrication, poor adherence, and only marginally improved corrosion resistance have rendered the prior art approaches incompletely acceptable. A somewhat thick film resulting from the prior art surface treatment is required in order to effect corrosion resistance and such films provide poor handling characteristics. The poor adherence of such thick finished coatings to the treated substrate compounds the problem even further.

Other processes have been employed to increase the resistance of metallic surfaces to corrosion, which processes include the use of an oxygenated organic compound. It is noted, however, that in each of these attempts, the compositions employed also contained additional ingredients such as polymeric materials, a multiplicity of reducing agents, fillers, and the like. As distinguished therefrom, the composition of the instant invention is a relatively simple one which includes a solution of the 3,679,493 Patented July 25, 1972 reaction product of a water soluble chromium compound with an oxygenated organic compound as the essential ingredient thereof. While other materials may be added to the instant composition, they are not essential to the effectiveness thereof.

Therefore, it is an object of the instant invention to provide improved corrosion resistant coatings for metallic surfaces.

Another object of the instant invention is to provide for a process of improving the corrosion resistance of metallic surfaces.

'THE INVENTION These and other objects of the instant invention are acheived by the provision of a corrosion-resistant coating consisting essentially of the reaction product of a water soluble chromium compound with an oxygenated organic compound in the presence of Water.

DETAILED DESCRIPTION The composition of the instant invention is considered particularly useful in protecting ferrous metallic surfaces in general such as iron and steel plate or castings, tin coated and zinc coated (galvanized) iron and steel and other ferrous alloys. Other metallic surfaces which may be protected by the composition and product of this invention include non-ferrous substrates such as zinc surfaces, aluminum surfaces, magnesium surfaces, tin surfaces, and non-ferrous alloy surfaces such as brass, bronze and the like.

As previously noted, one of the essential ingredients of the instant composition is a water-soluble chromium compound. The useful chromium compounds include, but are not limited to, chromium trioxide, ammonium chromate, zinc chromate, chromium chromate, chromic acid, potassium dichromate, and mixtures thereof. It is, of course, within the scope of the instant invention to employ other chromium salts similar to the above which are soluble in the reaction medium.

The useful oxygenated organic compounds generally have the formula:

R OCH HO L .in 1) wherein R represents an alkyl group having from 1 to 6 carbon atoms, R and -R represent hydrogen or an alkyl group having from 1 to 6 carbon atoms, and n is an integer of from 1 to 4. Representative of compounds included in the above general formula are the following:

In addition to the above two essential ingredients, i.e., the water-soluble chromium compound and the aforesaid oxygenated organic compound, one may also employ in connection with the composition of the instant invention various compatible wetting agents to improve the surface wetting and coating uniformity of said composition. It is noted that the Wetting agent employed must be one which is compatible with, and stable in the presence of, the chromium compound employed in the instant invention. Therefore, preferably, one employs as the wetting agent a nonionic or anionic surfactant material although other types of surfactants may also be employed if compatible under the conditions of use. Representative of the surfactants which may be employed are the following:

(1) Alkylaryl sulfonates such as sodium alkylnaphthalene sulfonate.

(2) Alkyl sulfates such as sodium lauryl sulfate.

(3) The sulfonated esters.

(4) Alkali salts of alkylaryl polyether sulfonates,

(5) The alkanesulfonates.

(6) Alkylphenyl polyethylene glycol ethers.

(7) Alkali salts of fluoro-substituted alkanesulfonates.

(8) Surfactants in which the hydrophilic fraction of the molecule is provided by ethylene oxide.

(9) Alkyl phosphates.

(10) Surfactant substituted amide reaction products of a carboxylic acid and ethanolamine.

(11) Surfactant C to C alkyl chain esters of polyoxyethylene glycol.

(12) Surfactant condensation products of a carboxylic acid and an amine.

(13) Monoether surfactants.

In addition to the surfactant, phosphoric acid may be added to the composition of the instant invention to increase, to some degree, the adhesion of the coating composition to the metallic surface.

The composition of the instant invention is prepared by admixing the water-soluble chromium compound delineated above with the oxygenated organic compound also delineated above in the presence of Water. While the exact reaction is unknown, it is though that the oxygenated organic compound forms an oxidized complex and this results in an improved corrosion resistant coating.

In general in the compositions of the instant invention it is preferred to employ from about 0.05 to about 50 percent by weight of the oxygenated organic compound and from about 0.5 to about 10 percent by weight of the water-soluble of the chromium compound. As previously noted, phosphoric acid, in amounts from about 0.5 percent to about 10 percent have been found to be useful. With regard to the wetting agents or surfactants, if employed, amounts from about 0.01 percent to about 1 percent by weight are adequate. Preferably, the compositions of the instant invention include from about 0.5 to about 10 percent of the glycol ether and from about 2 to about 7 percent of the water-soluble chromium compound.

The instant invention will be illustrated by the following detailed examples. It is to be noted, however, that the instant invention is not deemed as being limited thereto.

4 EXAMPLE 1 Coating formulations containing 20% glycol ether and 5.0% chromic acid were prepared by mixing equal volumes of the following two solutions.

Solution A: This solution, containing 40% glycol ether, was prepared by adding to a wide mouth jar.

- Grams Ethylene glycol monobutyl ether 40 Water 60 This mixture was shaken to dissolve at room temperature.

Solution B: A 10% solution of chromic acid in water was prepared by adding to a wide mouth jar.

Grams Chromium trioxide 10.0 Water 90.0

Grams Ethylene glycol monobutyl ether 24 Water 76 This mixture was shaken to dissolve at room temperature.

Solution D. This solution, containing 10.0% chromic acid and 1.0% phosphoric acid was prepared by adding to a wide mouth jar Grams Chromic trioxide 10.0 86% phosphoric acid 1.0 Water 89.0

This mixture was shaken to dissolve at room temperature.

Equal portions of Solutions C and D were mixed thoroughly at room temperature to give the desired coating formulation.

Solutions containing the other compositions listed in Table 1 were prepared in a similar fashion. The wetting agent, when used, was added by using the proper volume of a dilute (0.10%) aqueous solution of the wetting agent. Carbon steel (1010) panels were used for the rust inhibition test. These panels measured 3" x 8" x 0.051" and were cut from steel which had been cold rolled using rolls that yields a surface finish of 6-12 microinches. The panels had been protected from rusting with a vapor phase inhibitor and were used directly as received. The panels were dip-coated in the proper formulation, withdrawn from the solution and allowed to drain dry at room temperature. After standing at room temperature for 24 hours, the panels were placed in the QCT condensing humidity cabinet. The cabinet was operated with the water temperature at 131 F. and vapor temperature at F. Rusting was induced by the moisture which condensed continuously on the panels. The panels were observed daily for the appearance of rust spots and were rated as follows. A perimeter approximately A" wide was excluded from observation. A test surface passed if it contained no more than three dots of rust, no one of which was greater than 1 mm. in diameter. A test surface failed if it contained one or more dots of rust larger than 1 mm. in diameter or if it contained four or more dots of any size. The number of days protection obtained (days with no rust spots appearing) was a measure of product performance.

Table 1 shows the number of days of rust protection afforded to panels which had been coated with the rust inhibiting compositions described.

TABLE 1.--NUMBER OF DAYS OF RUST PROTECTION OBTAINED WITH COATINGS PREPARED WITH ETHYLENE GLYGOL MONO BUTYL ETHER CHROMIUM TRIOXIDE, PHOSPHORIC ACID OR WETTING AGENT AND WATER 1 Commercial syrupy phosphoric acid containing 85-87% HaPO4.

I Two m1. of a 0.1% aqueous solution of nonyiphenoxypoly (ethyleneoxy) ethanol.

8 Ethylene glycol monoisobutyl ether.

As will readily be seen from a study of the above table, placed, after various times of drying at room temperathe panels coated with ethylene glycol monobutyl ether ture or after oven curing from 10-15 minutes at 100 C., and water, i.e., Test No. 1, showed evidence of rusting in in the QCT cabinet for determination of rust protection. less than 1 day and, in fact, in less than 1 hour. The Table 2shows the number of days rust protection obtained panels coated with only chromic acid and water demonwith these coatings prepared with the mono methyl and strated rusting within 1 day. In contrast therefrom, hoW- ethyl ethers of ethylene glycol, the mono methyl, ethyl ever, panels coated with the composition of the instant and butyl ethers of diethylene glycol, and the mono proinvention, i.e., a composition comprising a glycol ether, pyl together with chromium trioxide, and phosphoric acid a chromium compound and water, were protected from or wetting agent. rusting for a period of at least 4 days and in most in- Five to greater than 10 days rust protection was obstances for a substantially longer period. tained with all of these products.

TABLE 2.NUMBER OF DAYS OF RUST PROTECTION IN THE QCT CABINET OBTAINED WITH COATINGS PREPARED WITH DIFFERENT GLYCOL ETHERS, CHROMIUM TRIOXIDE, PHOSPHORIC ACID OR A WETTING AGENT AND WATER Percent compositions of coating formulation Oven dried Air dried panels panels 10-15 Phosmin. at 100 0., Chromium Wetting phoric Hours Days rust days rust Glycol ether, concentration trioxide agent 1 acid Water drying protection protection 5% ethylene glycol mono methyl ether 5 1 89 96 10 10 5% ethylene glycol mono ethyl ether 5 1 89 96 10 10 5% diethylene glycol mono methyl 0 5 1 89 120 10 10 5% diethylene glycol mono ethyl ether. 5 1 89 120 10 10 5% diethylene glycol mono butyl ether-.- 5 1 89 120 10 10 5% propylene glycol mono propyl ether 5 89 120 6 6 20% propylene glycol mono propyl ether 5 74 120 5 10 1 N onylphenoxypoly (ethyleneoxy) ethanol containing 64% ethylene oxide.

EXAMPLE 2 Coating formulations containing glycol ether and EIQKMPLE 4 5.0% chromic trioxide were prepared by adding to a wide Aqueous coating solutions were prepared using chrommouth jar lum trioxlde and the triand tetraethylene glycols listed Grams in Table 3. Panels were air dried for 24, 120, or 168 Ethylene glycol monobutyl ether 50 50 hours and were oven cured for 15 min. at 100 C. The

Water 45 days rust protection obtained are listed in Table 3.

TABLE 3:NU1VIBER OF DAYS RUST PROTECTION IN QCT CABINET OBTAINED WITH COATINGS PREPARED WITH TRI- AND TETRAETHYLENE GLYCOL ETHERS Percent composition of coating Days of protection from rust,

QCT cabinet formulation Air dried panels Panels oven Chromium Wetting Hours Days rust dried 100 C.

trioxide agent Water drying protection 15 min 5% triethylene glycol dimethyl ether 5 1 89 120 10 10 5% tetraethylene glycol dimethyl ether 5 1 89 120 10 10 5% triethylene glycol monomethyl ether- 5 1 89 120 10 10 5% triethylene glycol mono ethyl ether- 5 1 89 120 10 10 5% triethylene glycol mono butyl ether- 5 1 89 168 10 10 This mixture was shaken to dissolve at room tempera- EXAMPLE 5 ture. After solution had been obtained 5.0 grams of chromium trioxide was added, Panels were coated with formulations having the com- The mixture was shaken at room temperature t dispositions listed in Table 4, and were dried as described sol in the table headings. After drymg, they were subject to Panels were then coated, dried at room temperature impact using a four'pound hammer pp from a height for 24 hours and tested as described in Example 1. Rust required to give 70 80 inch-Pounds impact The protection of 13 days was obtained. mer had a hemispherical head which was /2" in diameter.

EXAMPLE 3 These panels were then placed in the QCT cabinet to determine rust protection on the stressed surface. Observa- Coating solutions having the compositions listed in tions were also made on theplane panel surface. The days Table 2 were prepared as described in Example 1 and protection obtained are listedinTabie 3.

Examination of the data shows that excellent rust protection was obtained on the impacted surface.

What is claimed is: 1. A corrosion-resistant coating composition consisting TABLE 4.-NUMBER OF DAYS RUST PROTECTION IN'QCT CABINET AT 120 F. VAPOR TEMPERATURE Days rust Protection I e Impacted Area Plane area Monobutyl- Air drie Oven dried ether of Ethoxy- 120 hrs. 100 0., 15 min ethylene Ethoxylated Oven dried glycol, Percent Percent lated alkyl- Percent 70 80 70 '80 Air dried 110-110" 0., Formulation ref. percent CrO; H 04 alcohol 1 phenol I water in.-lb in.-lb. in.-lb. in.-lb. 120 hrs 15 m Cir-1a alcohol plus 70% ethyleneoxide.

EXAMPLE 6 TABLE 5.RUST PROTECTION BY ETHERS OF TRIETHYL- ENE GLYCOL, COATING COMPOSITION, PERCENT All formulations contained 5.0% glycol ether, 5.0% 0103, and 89.0%

water Days rust protection in QCT cabinet Oven dried Glycol ether Wetting Air dried 15 min., RO(C2H40)3H H PO| agent 1 48-120 hrs. 100 0.

R=Methy1 0. 0 1. 0 21 21 R=butyl 0.0 1. 0 21 21 lqonylphenoxypoly (ethyleneoxy) ethanol containing 64% ethylene ex ea.

As will readily be seen from a study of Table 5, the compositions of the instant invention, including phosphoric acid and a wetting agent, provided superior rust protection.

EXAMPLE 7 Coating formulations were prepared as in Example 1 containing 5.0% and 20.0% of the dimethyl ethers of triand tetraethylene glycol with 5.0% chromic acid. Some of the solutions contained phosphoric acid; some of them contained a wetting agent. The composition and performance data are shown in Table 6. Some panels were air dried for 24-120 hours; some were oven dried for 15 min. at 100 C.

TABLE 6.-RUST PROTECTION BY DIMETHYL ETHERS OF TRI- AND essentially of the product of the reaction in the presence of water, of a water-soluble chromium compound and a compound having the formula;

R1 R2 mongre L J. (I)

wherein R is an alkyl group having from 1 to 6 carbon atoms, R and R are selected from the group consisting of hydrogen and an alkyl group having from 1. to 6 carbon atoms, and n is an integer of from 1 to 4; said chromium compound being present in an amount of from about 0.5 to about 10% by weight and said compound of Formula I being present in an amount of from about 0.5 to about 50% by weight. 2. The composition of claim 1 wherein said chromium compound is present in an amount of from about 2 to about 7% by weight.

3. The composition of claim 1 wherein said compound of FormulaI is present in an amount of from 0.5 to about 10% by weight.

4. The composition of claim 1 aqueous solution thereof.

5. A corrosion-resistant coating composition according to claim 1 additionally including at least one member selected from the group consisting of phosphoric acid, and compatible anionic and non-ionic surfactants.

6. The composition of claim 5 wherein the water-soluble chromium compound is chromium trioxide.

7. The composition of claim 5 wherein the compound having the structure of Formula I is the monobutyl ether of ethylene glycol.

8. The composition of claim 5 wherein the compound of Formula I is the monoalkyl ether'of ethylene glycol.

9. The composition of claim 5 wherein the compound having the structure of Formula 6 is the monoalkyl ether of diethylene glycol.

10. The composition of claim 5 wherein the compound having the structure of Formula I is the monoalkyl ether of propylene glycol.

in the form of an TETRAETHYLENE, GLYCOL O OATIN G 0 0M]? OSITION, PE ROENT All formulations contained 5.0% C103 and sufiicient water to make 100.00%

l Nonylphenoxypoly (ethyleneoxy) ethanol containing 64% ethylene oxide.

Once again, it will readily be noted that the compositions of the instant invention provide a surprising and unexpected rust protection for metallic surfaces.

11. The composition of claim 5 wherein the compound having the structure of Formula I is the monoalkyl ether of triethylene glycol.

12. The composition of claim wherein the phosphoric acid is present in an amount of from about .05 to about percent.

13. The composition of claim 5 wherein the surfactant is present in an amount of from about 0.01 to about 1 percent.

14. The composition of claim 5 wherein the compound having the structure of Formula I is monobutyl ether of ethylene glycol.

15. A process for improving the corrosion resistance of metallic surfaces which comprise contacting a metallic surface with a composition according to claim 1 whereby there is formed a corrosion-resistant film upon said surface and allowing said film to dry thereon.

16. The process of claim wherein said composition is in the form of an aqueous solution thereof.

17. A process for improving the corrosion resistance of metallic surfaces according to claim 15 wherein said composition additionally contains at least one member selected from the group consisting of phosphoric acid and anionic and non-ionic surfactants.

18. The process of claim 15 wherein the chromium compound is chromium trioxide.

19. The process according to claim 15 wherein the drying is eflected at temperatures in the range from room temperature up to C.

20. The process of claim 17 wherein the phosphoric acid is present in an amount of from about .05 to about 10 percent.

21. The process of claim 17 wherein the surfactant is present in an amount of from about 0.01 to about 1 percent.

References Cited UNITED STATES PATENTS 2,662,835 12/1953 Reid 252-396 3,189,489 6/1965 Schifiman l48-6.16 3,218,265 11/1965 Rink et al. 252-389 3,279,958 10/1966 Maurer et a1. l486.l6 3,445,400 5/1969 Everhart 21-2.7

FOREIGN PATENTS 683,154 ll/l952 Great Britain 252-389 LEON D. ROSDOL, Primary Examiner I. GLUCK, Assistant Examiner US. Cl. X.R. 

